The phenomenon of the shrinking size of bank vole (Myodes glareolus) in an anthropogenic environment (experience of 50 years of observations)

  • S. A. Мyakushko Taras Shevchenko National University of Kyiv
Keywords: size and mass parameters; shrinking; population dynamics; ecological balance.


Fifty years of continuous monitoring of the bank vole population (Myodes glareolus Schreber, 1780) revealed the phenomenon of shrinking body size of individuals, manifesting in significant reduction in their regular size and mass parameters. Field observations were carried out in the Kaniv Nature Reserve (Cherkasy region, Ukraine) during the first half of summer every year. In the forest biotopes of the reserve, this species is dominant in the group of rodents. The research period covered various stages of the existence of the protected ecosystem. Its small area, location ina densely populated region of Ukraine and interaction with neighboring territories which are involved in economic activities have always caused anthropogenic pressure on the protected area. Its nature and intensity determined the changes in the protection regime and the loss of reserve status in 1951–1968. Later, the territory of the reserve experienced increasing technogenic pressure accompanied by radioactive contamination. In this work, to compare their characteristics, four complete cycles of the density dynamics of the bank vole population (from depression to depression) were selected, the duration of which was 4–5 years. The first three cycles correspond to qualitatively different periods in the existence of the ecosystem and the population of the studied species, and the last one corresponds to the relatively current situation. Over the recent 30 years, the size and mass parameters of individuals of bank voles have deсreased, - this phenomenon was called shrinking. The process was also observed to tend towards consistent increase in scale. Differentiated analysis shows that in different sex and functional groups of animals, the decrease in exterior parameters can reach 30.3%. Shrinking is especially notable in the group of adult females that are actively involved in reproduction (compared to the second cycle, considered as the control, the decrease in parameters among these is 33.2%). Juveniles of this sex lost 31.8% of their fatness. Besides, in the population of voles, the proportion of large-size individuals was significantly reduced. The group of animals that overwintered significantly reduced its representation, and its existing representatives had much smaller exterior parameters. The studies found that the shrinking process is stable over time, which does not allow it to be considered a random phenomenon or an artifact of research. This phenomenon has no correlation with the amount or availability of food. It occurs against the background of numerous changes in various aspects of population dynamics, which gives grounds to associate it with anthropogenic changes in the environment. Shrinking is believed to be realized through various mechanisms. Firstly, as a result of mortality, the largest individuals and reproducing females with the greatest energy needs disappear from the population, and secondly, the growth and weight gain of young animals is slower. As a result, decrease in the size and mass parameters of individuals reduces their specific energy needs and allows the population to bring their requirements in correspondance with the capability of the environment to support a certain number of resource consumers. An analogy was drawn with the Dehnel’s phenomenon, described for shrews of the Sorex genus, whose body size and weight decrease is an element of preparation for experiencing adverse winter conditions. Based on similar concepts, the shrinking of its elements can be considered as a specific population strategy to maintain the ecological balance.


Aalto, J., & Lampinen, J. (2015). A population adaptation mechanism for differential evolution algorithm. 2015 IEEE Symposium Series on Computational Intelligence, 2015, 1514–1521.

Andreassen, H. P., Sundell, J., Ecke, F., Halle, S., Haapakoski, M., Henttonen, H., Huitu, O., Jacob, J., Johnsen, K., Koskela, E., Luque-Larena, J. J., Lecomte, N., Leirs, H., Mariën, J., Neby, M., Rätti, O., Sievert, T., Singleton, G. R., van Cann, J., Broecke, B. V., & Ylönen, H. (2021). Population cycles and outbreaks of small rodents: Ten essential questions we still need to solve. Oecologia, 195, 601–622.

Benincà, E., Ballantine, B., Ellner, S. P., & Huisman, J. (2015). Species fluctuations sustained by a cyclic succession at the edge of chaos. Proceedings of the National Academy of Sciences of the United States of America, 112(20), 6389–6394.

Bian, J.-H., Du, S.-Y., Wu, Y., Cao, Y., Nie, X., He, H., & You, Z. (2015). Maternal effects and population regulation: Maternal density-induced reproduction suppression impairs offspring capacity in response to immediate environment in root voles Microtus oeconomus. Journal of Animal Ecology, 84, 326–336.

Brouard, M. J., Knowles, S. C. L., Dressen, S., Coulson, T., & Malo, A. F. (2020). Factors affecting woodland rodent growth. Journal of Zoology, 312(3), 174–182.

Dehnel, A. (1949). Badania nad rodzajem Sorex L. [Research on the genus Sorex L.]. Annales Universitatis Mariae Curie-Sklodowska, sectio C, 4(2), 17–97 (in Polish).

Efford, M. G., Fitzgerald, M., Karl, B. J., & Berben, P. H. (2006). Population dynamics of the ship rat Rattus rattus L. in the Orongorongo Valley, New Zealand. New Zealand Journal of Zoology, 33(4), 273–297.

Egerton, F. N. (2015). History of ecological sciences. Part 55: Animal population ecology. The Bulletin of the Ecological Society of America, 96(4), 560–626.

Ergon, T., & Ergon, R. (2016). When three traits make a line: Evolution of phenotypic plasticity and genetic assimilation through linear reaction norms in stochastic environments. Journal of Evolutionary Biology, 30, 486–500.

Fay, R., Barbraud, C., Delord, K., & Weimerskirch, H. (2016). Variation in the age of first reproduction: Different strategies or individual quality? Ecology, 97, 1842–1851.

Ferrari, M., Lindholm, A. K., & König, B. (2019). Fitness consequences of female alternative reproductive tactics in house mice (Mus musculus domesticus). The American Naturalist, 193(1), 106–124.

Finn, K. T., Parker, D. M., Bennett, N. C., & Zöttl, M. (2018). Contrasts in body size and growth suggest that high population density results in faster pace of life in Damaraland mole-rats (Fukomys damarensis). Canadian Journal of Zoology, 96(8), 920–927.

Gómez Fernández, M. J., Boston, E. S., Gaggiotti, O. E., Kittlein, M. J., & Mirol, P. M. (2016). Influence of environmental heterogeneity on the distribution and persistence of a subterranean rodent in a highly unstable landscape. Genetica, 144(6), 711–722.

Grishchenko, A. M., Ostapenko, V. G., & Grishchenko, S. A. (1993). Kartograficheskiye dannyye opredeleniya urovney summarnogo tekhnogennogo zagryazneniya okruzhayushchey sredy po embriotoksichnosti i teratogennosti donnykh otlozheniy i pochv chasti territorii Ukrainy do i posle avarii na Chernobyl’skoy AES [Cartographic data on the determination of the levels of total technogenic pollution of the environment by embryotoxicity and teratogenicity of bottom sediments and soils of a part of the territory of Ukraine before and after the accident at the Chernobyl Nuclear Power Plant]. Reports of the National Academy of Sciences of Ukraine, 1, 127–134 (in Russian).

Hope, A. G., Waltari, E., Dokuchaev, N. E., Abramov, S., Dupal, T., Tsvetkova, A., Henttonen, H., MacDonald, S. O., & Cook, J. A. (2010). High-latitude diversification within Eurasian least shrews and Alaska tiny shrews (Soricidae). Journal of Mammalogy, 91(5), 1041–1057.

Krebs, C. (1996). Population cycles revisited. Journal of Mammalogy, 77(1), 8–24.

Lázaro, J., Hertel, M., Sherwood, C. C., Muturi, M., & Dechmann, D. K. N. (2018). Profound seasonal changes in brain size and architecture in the common shrew. Brain Structure and Function, 223, 2823–2840.

Lázaro, J., Nováková, L., Hertel, M., Taylor, J., Muturi, M., Zub, K., & Dechmann, D. (2021). Geographic patterns in seasonal changes of body mass, skull, and brain size of common shrews. Ecology and Evolution, 11(6), 2431–2448.

Letnic, M., & Dickman, C. R. (2010). Resource pulses and mammalian dynamics: Conceptual models for hummock grasslands and other Australian desert habitats. Biological Reviews, 85(3), 501–521.

Lidicker Jr., W. Z. (2020). Reproductive adaptations to high densities in social mammals. Therya, 11(3), 440–446.

Mezhzherin, V. A. (1964). Yavleniye Denelya i yego vozmozhnoye ob’yasneniye [Denel’s phenomenon and its possible explanation]. Acta Theriologica, 8(6), 95–114 (in Russian).

Mezhzherin, V. A., & Miakushko, S. A. (1998). Strategii populiatsij melkikh gryzunov Kanevskogo zapovednika v uslovijakh izmenennoj sredy obitanija pod vozdejstviem tekhnogennykh zagriaznenij i avarii na ChAES [Strategy of small rodent populations from Kaniv Nature Reserve under habitat changes caused by technogenic pollutions and the accident at the Chernobyl Nuclear Power Plant]. Izvestija Akademii Nauk, Seriia Biologicheskaia, 3, 374–381 (in Russian).

Mezhzherin, V. A., Emelyanov, I. G., & Mihalevich, O. A. (1991). Kompleksnyje podkhody v izucheniju populyatsij melkikh mlekopitayushchikh [Comprehensive approaches in studying of populations of small mammals]. Naukova Dumka, Kyiv (in Russian).

Mezhzherin, V. A., Myakushko, S. A., & Semenyuk, S. K. (2002). Population as a test system. Biology Bulletin, 29(5), 519–524.

Myakushko, S. A. (1998). Izmeneniye dinamiki populyatsiy i soobshchestva gryzunov v rezul’tate antropogennogo vozdeystvija na zapovednuyu ekosistemu [Changes in the dynamics of populations and communities of rodents as a result of anthropogenic impact on a protected ecosystem]. Vestnik Zoologii, 32(4), 76–85 (in Russian).

Myakushko, S. A. (2001). Strategii vosproizvodstva v populyatsiyakh gryzunov [Reproduction strategies in rodent populations]. Uchenyye Zapiski Tavricheskogo Natsionalnogo Universiteta, Seriya Biologicheskaya, 14(2), 129–133 (in Russian).

Myakushko, S. A. (2002). Bahatorichna dynamika populyatsiy hryzuniv yak kryteriy stanu seredovyshcha [Long-term dynamics of populations of rodents as a criterion of the environment]. Visnyk Lvivskoho Universytetu, Seriya Biolohichna, 30, 30–34 (in Ukrainian).

Myakushko, S. A. (2005). Zminy masy ta rozmiriv tila hryzuniv v umovakh riznykh form antropohennoho navantazhennya [Changes in body weight and body size of rodents under various forms of anthropogenic load]. Zapovidna Sprava v Ukrajini, 11, 34–40 (in Ukrainian).

Myakushko, S. A. (2016). Spivvidnoshennya riznykh form minlyvosti v populyatsiyakh dvokh vydiv noryts’ [The ratio of different forms of variability in populations of two species of voles]. Naukovi Zapysky Ternopil’s’koho Natsional’noho Pedahohichnoho Universytetu imeni Volodymyra Hnatyuka, Serija Biologija, 67, 84–90 (in Ukrainian).

Myakushko, S. A. (2018). Heterohennist’ populyatsiy hryzuniv na terminal’nykh fazakh dynamiky shchil’nosti [Heterogeneity of rodent populations during terminal phases of density dynamics]. Ukrainian Journal of Ecology, 8(1), 97–102 (in Ukrainian).

Olenev, G. V. (2002). Alternative types of ontogeny in cyclomorphic rodents and their role in population dynamics: An ecological analysis. Russian Journal of Ecology, 5, 321–330.

Orlov, О. О. (1998). Meta, zavdannya i metody radioekolohichnykh doslidzhen’ u pryrodnykh zapovidnykakh Ukrajiny, yaki zaznaly radioaktyvnoho zabrudnennya vnaslidok Chornobyl’s’koji katastrofy [Goals, objectives and methods of radioecological research in nature reserves of Ukraine, which are contaminated by the Chernobyl accident]. Zapovidna Sprava v Ukrayini, 4(2), 65–68 (in Ukrainian).

Ozgul, A., Childs, D. Z., Oli, M. K., Armitage, K. B., Blumstein, D. T., Olson, L. E., Tuljapurkar, S., & Coulson, T. (2010). Coupled dynamics of body mass and population growth in response to environmental change. Nature, 466, 482–485.

Pacifici, M., Santini, L., Di Marco, M., 1, Baisero, D., Francucci, L., Marasini, G. G., Visconti, P., & Rondinini, C. (2013). Generation length for mammals. Nature Conservation, 5, 89–94.

Pirotta, E., Mangel, M., Costa, D. P., Goldbogen, J., Harwood, J., Hin, V., Irvine, L. M., Mate, B. R., McHuron, E. A., Palacios, D. M., Schwarz, L. K., & New, L. (2019). Anthropogenic disturbance in a changing environment: Modelling lifetime reproductive success to predict the consequences of multiple stressors on a migratory population. Oikos, 128(9), 1340–1357.

Prevedello, J. A., Dickman, C. R., Vieira, M. V., & Vieira, E. M. (2013). Population responses of small mammals to food supply and predators: A global meta-analysis. Journal of Animal Ecology, 82(5), 927–936.

Read, Q. D., Grady, J. M., Zarnetske, P. L., Record, S., Baiser, B., Belmaker, J., Tuanmu, M., Strecker, A., Beaudrot, L., & Thibault, K. M. (2018). Among-species overlap in rodent body size distributions predicts species richness along a temperature gradient. Ecography, 41(10), 1718–1727.

Rödel, H. G., Valencak, T. G., Handrek, A., & Monclús, R. (2016). Paying the energetic costs of reproduction: Reliance on postpartum foraging and stored reserves. Behavioral Ecology, 27(3), 748–756.

Rödel, H. G., Zapka, M., Talke, S., Kornatz, T., Bruchner, B., & Hedler, C. (2015). Survival costs of fast exploration during juvenile life in a small mammal. Behavioral Ecology and Sociobiology, 69, 205–217.

Romero-Mujalli, D., Rochow, M., Kahl, S., Paraskevopoulou, S., Folkertsma, R., Jeltsch, F., & Tiedemann, R. (2021). Adaptive and nonadaptive plasticity in changing environments: Implications for sexual species with different life history strategies. Ecology and Evolution, 11, 6341–6357.

Rozenberg, G. S., & Ryansky, F. N. (2005). Teoreticheskaja i prikladnaja ekologija [Theoretical and applied ecology]. Publishing House of Nizhnevartovsk State University, Nizhnevartovsk (in Russian).

Rozenberg, G. S., Ryansky, F. N., Lazareva, N. V., Saksonov, S. V., Simonov, Y. V., & Khasaev, G. R. (2016). Obshchaya i prikladnaya ekologiya [General and applied ecology]. Samara State Economic University Press, Samara, Tolyatti (in Russian).

Selås, V., Kobro, S., & Sonerud, G. (2013). Population fluctuations of moths and small rodents in relation to plant reproduction indices in southern Norway. Ecosphere, 4(10), 1–11.

Shenbrot, G. (2014). Population and community dynamics and habitat selection of rodents in complex desert landscapes. Mammalia, 78(1), 1–10.

Sobral, G., & de Oliveira, A. J. (2014). Annual age structure and reproduction in the Caatinga red-nosed mouse, Wiedomys pyrrhorhinos (Rodentia, Sigmodontinae). Therya, 5(2), 509–534.

Soininen, E. M., Henden, J. A., Ravolainen, V. T., Yoccoz, N. G., Bråthen, K. A., Killengreen, S. T., & Ims, R. A. (2018). Transferability of biotic interactions: Temporal consistency of arctic plant-rodent relationships is poor. Ecology and Evolution, 8(19), 9697–9711.

Speakman, J. R. (2008). The physiological costs of reproduction in small mammals. Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences, 363(1490), 375–398.

Terry, R. C., & Rowe, R. J. (2015). Energy flow and functional compensation in Great Basin small mammals under natural and anthropogenic environmental change. Proceedings of the National Academy of Sciences of the United States of America, 112(31), 9656–9661.

Torre, I., & Arrizabalaga, A. (2008). Habitat preferences of the bank vole Myodes glareolus in a Mediterranean mountain range. Acta Theriologica, 53, 241–250.

Wilson, D., Innes, J., Fitzgerald, N., Bartlam, S., Watts, C., & Smale, M. (2018). Population dynamics of house mice without mammalian predators and competitors. New Zealand Journal of Ecology, 42(2), 192–203.

Xu, M. (2016). Ecological scaling laws link individual body size variation to population abundance fluctuation. Oikos, 125, 288–299.

Yakimov, B. N., Solntsev, L. A., Rozenberg, G. S., Iudin, D. I., & Gelashvili, D. B. (2014). Scale invariance of biosystems: From embryo to community. Russian Journal of Developmental Biology, 45, 168–176.